Chipiso Kudzanai, Simoyi Reuben H
Department of Chemistry, Portland State University , Portland, Oregon 97207-0751, United States.
School of Chemistry and Physics, University of KwaZulu-Natal , Westville Campus, Durban 4014, South Africa.
J Phys Chem A. 2016 Jun 2;120(21):3767-79. doi: 10.1021/acs.jpca.6b02699. Epub 2016 May 23.
The kinetics and mechanism of the oxidation of methimazole (1-methyl-3H-imidazole), MMI, by chlorite in mildly acidic environments were studied. It is a complex reaction that gives oligo-oscillations in chlorine dioxide concentrations in excess chlorite conditions. The stoichiometry is strictly 2:1, with the sulfur center being oxidized to sulfate and the organic moiety being hydrolyzed to several indeterminate species. In excess MMI conditions over chlorite, the sulfinic acid and sulfonic acid were observed as major intermediates. The sulfenic acid, which was observed in the electrochemical oxidation of MMI, was not observed with chlorite oxidations. Initial reduction of chlorite produced HOCl, an autocatalytic species in chlorite oxidations. HOCl rapidly reacts with chlorite to produce chlorine dioxide, which, in turn, reacts rapidly with MMI to produce more chlorite. The reaction of chlorine dioxide with MMI is competitive, in rate, with the chlorite-MMI and HOCl-ClO2(-) reactions. This explains the oligo-oscillations in ClO2 concentrations.
研究了在弱酸性环境中，亚氯酸盐氧化甲巯咪唑（1-甲基-3H-咪唑，MMI）的动力学和机理。这是一个复杂的反应，在过量亚氯酸盐条件下，二氧化氯浓度会出现寡聚振荡。化学计量比严格为2:1，硫中心被氧化为硫酸盐，有机部分水解为几种不确定的物质。在甲巯咪唑过量于亚氯酸盐的条件下，亚磺酸和磺酸被观察到是主要中间体。在甲巯咪唑的电化学氧化中观察到的亚磺酸，在亚氯酸盐氧化中未被观察到。亚氯酸盐的初始还原产生次氯酸，这是亚氯酸盐氧化中的一种自催化物质。次氯酸迅速与亚氯酸盐反应生成二氧化氯，而二氧化氯又迅速与甲巯咪唑反应生成更多的亚氯酸盐。二氧化氯与甲巯咪唑的反应在速率上与亚氯酸盐-甲巯咪唑和次氯酸-二氧化氯（-）反应具有竞争性。这解释了二氧化氯浓度的寡聚振荡。
